Optogenetics is a research method involving the stimulation or inhibition of target neurons using specific wavelengths of light. Optogenetics can affect the measured membrane potential by activating neurons (i.e., causing them to experience an increase in membrane potential) or inhibiting neurons (i.e., causing them to experience a decrease in membrane potential). A researcher will implant fiber-optic cable to deliver specific wavelengths of light to targeted neurons. When these wavelengths of light reach the targeted neurons, they stimulate special light-sensitive proteins called opsins, which proceed to open ion channels that either active or inhibit the targeted neurons. Note that opsins that can directly stimulate the opening of ion channels are not native to mammalian neurons, rather, mammalian neurons are genetically induced to produce microbial opsins that can accomplish this function.